Objective: In recent years, infections caused by Escherichia coli (E.coli) and Klebsiella pneumoniae (K.pneumoniae) have increased in intensive care units (ICUs), and their high resistance to many antibiotics has made their treatment difficult. The aim of this study was to determine the frequency and antibiotic resistance rates of E.coli and K.pneumoniae strains isolated from patients hospitalized in our hospital\'s ICU.

Material and Method: In this study, E.coli and K.pneumoniae strains isolated from clinical samples sent from ICUs to microbiology laboratory between 2016-2020, were included. Bacterial identification and antibiotic susceptibility tests were performed using conventional methods and automated systems.

Results: A total of 1154 E.coli and 924 K.pneumoniae isolates were included in the study. Among the gram-negative bacteria, E.coli and K. pneumoniae strains were detected as the first and the second most common respectively. Both microorganisms were isolated most frequently from urine samples and secondly from endotracheal aspirate samples. The highest resistance rates were to amoxicillin-clavulanate, ceftriaxone, trimethoprimsulfamethoxazole and ciprofloxacin. It was observed that ESBL positivity was higher in E.coli strains, carbapenem and piperacillin-tazobactam resistance was much higher in K.pneumonia. Also, the resistance rates have changed over the years.

Conclusion: High rates of antibiotic resistance seen in gram-negative bacteria reduce the success of the treatment. For this reason, regular follow-up of their resistance surveillance and determining treatment protocols will contribute to the decrease in resistance.